Oxy-coal combustion has different flue gas composition from the conventional air-coal combustion. The different composition further results in different properties, such as the absorption coefficient, emissivity, and density, which can directly affect the heat transfer in both radiation and convection zones of utility boilers. This paper numerically studied a utility boiler of oxy-coal combustion and compares with air-coal combustion in terms of flame profile and heat transferred through boiler side walls in order to understand the effects of different operating conditions on oxy-coal boiler retrofitting and design. Based on the results, it was found that around 33 vol% of effective O-2 concentration ([O-2](effective)) the highest flame temperature and total heat transferred through boiler side walls in the oxy-coal combustion case match to those in the air-coal combustion case most; therefore, the 33 vol% of [O-2](effective) could result in the minimal change for the oxy-coal combustion retrofitting of the existing boiler. In addition, the increase of the moisture content in the flue gas has little impact on the flame temperature, but results in a higher surface incident radiation on boiler side walls. The area of heat exchangers in the boiler was also investigated regarding retrofitting. If boiler operates under a higher [O-2](effective), to rebalance the load of each heat exchanger in the boiler, the feed water temperature after economizer can be reduced or part of superheating surfaces can be moved into the radiation zone to replace part of the evaporators.

The techno-economic evaluation of the evaporative gas turbine (EvGT) cycle with two different CO2 capture options has been carried out. Three studied systems include a reference system: the EvGT system without CO2 capture (System I), the EvGT system with chemical absorption capture (System II), and the EvGT system with oxyfuel combustion capture (System III). The cycle simulation results show that the system with chemical absorption has a higher electrical efficiency (41.6% of NG LHV) and a lower efficiency penalty caused by CO2 capture (10.5% of NG LHV) compared with the system with oxyfuel combustion capture. Based on a gas turbine of 13.78 MW, the estimated costs of electricity are 46.1 $/MW h for System I, while 70.1 $/MW h and 74.1 $/MW h for Systems II and III, respectively. It shows that the cost of electricity increment of chemical absorption is 8.7% points lower than that of the option of oxyfuel combustion. In addition, the cost of CO2 avoidance of System II which is 71.8 $/tonne CO2 is also lower than that of System III, which is 73.2 $/tonne CO2. The impacts of plant size have been analyzed as well. Results show that cost of CO2 avoidance of System III may be less than that of System II when a plant size is larger than 60 MW.

Introducing CO2 capture and storage (CCS) into the power systems requires the re-investigation of the load balance for the electrical grid. For the oxy-coal combustion capture technology, the energy use of ASU can be shifted between the peak-load and off-peak-load periods, which may bring more benefits. In this paper, peak and off-peak (POP) operations for the air separation unit (ASU) with liquid oxygen storage were studied based on a 530 MW coal-fired power system. According to the simulation results, the oxy-coal combustion power system running POP is technically feasible that it can provide a base load of 496 MW during the off-peak period and a peak load of 613 MW during the peak period. And the equivalent efficiency of the power system running POP is only 0.3% lower than the one not running POP. Moreover, according to the economic assessments based on the net present value, it is also economically feasible that the payback time of the investment of the oxy-coal combustion power system running POP is about 13 years under the assumptions of 10% discount rate and 2.5% cost escalation rate. In addition, the effects of the difference of on-grid electricity prices, daily peak period, investment for POP operations, and ASU energy consumption were also analyzed, concerning the net present value.

Oxy-coal combustion is one of the technical solutions for mitigating CO2 in thermal power plants. For designing a technically viable and economically effective CO2 capture process, effects by coals and configurations of flue gas cleaning steps are of importance. In this paper, characterization of the flue gas recycle (FGR) is conducted for an oxy-coal combustion process. Different configurations of FGR as well as cleaning units including electrostatic precipitators (ESP), flue gas desulfurization (FGD), selective catalytic reduction (SCR) deNOx and flue gas condensation (FGC) are studied for the oxy-coal combustion process. In addition, other important parameters such as FGR rate and FGR ratio, flue gas compositions, and load of flue gas cleaning units are analyzed based on coal properties and plant operational conditions.

Oxy-fuel combustion is one of potential technologies for carbon dioxide (CO2) capture in fossil fuel fired power plants. Characterization of flue gas composition in the oxy-fuel combustion differs from that of conventional air-coal combustion, which results in the change of radiative heat transfer in combustion processes. This paper presents a numerical study of radiation intensity on lateral walls based on the experimental results of a 0.5MW combustion test facility (CTF). Differences in the oxy-coal combustion are analyzed, such as flue gas recycle, absorption coefficient and radiation intensity. The simulation results show that an effective O2 concentration ([O2]effective) between 29 and 33vol% (equivalent to the flue gas recycle ratio of 72-69%) constitutes a reasonable range, within this range the behavior of oxy-coal combustion is similar to air-coal combustion. Compared with the air-coal combustion, the lower limit (29vol%) of this range results in a similar radiative heat flux at the region closed to the burner, but a lower radiative heat flux in the downstream region of the CTF; the upper limit (33vol%) of this range results in a higher radiative heat flux at the region closed to the burner, while a similar radiative heat flux in the downstream region of the CTF.

This paper examined and assessed various configuration options about emission removal including particles, SO x and NO x in an oxy-coal combustion system for CO 2 capture. A performance analysis was conducted in order to understand the impacts of those options concerning process design, process operation and system efficiency. Results show that different flue gas recycle options have clear effects on the emissivity and absorptivity of radiating gases in boiler due to the change of flue gas compositions. The maximum difference amongst various options can be up to 15% and 20% for emissivity and absorptivity respectively. As a result, the heat transfer by radiation can vary about 20%. The recycle options also have impacts on the design of air heater and selective-catalytic-reduction (SCR) preheater. This is due to that the largely varied operating temperatures in different options may result in different required areas of heat exchangers. In addition, the dew point of flue gas and the boiler efficiency are affected by the configurations of flue gas recycle as well.

To combine the abilities of lipids extraction and CO2 capture by algae + IL system, chlorella hydrolysis integrating CO2 removal by ILs ([bmim][BF4], [bmim]Cl and [amim]Cl) to extract lipids energy-efficiently was demonstrated in this study. The addition of CO2 to [bmim][BF4] can increase the lipids yield from 14.2% to 15.6%. The value of net energy gain increased from 10.4 to 35.9 with the CO2 addition to [bmim][BF4] because of the compensated CO2 capture energy in the algae extraction process.

Thermodynamic properties of the air-water mixture at elevated temperatures and pressures are of importance in the design and simulation of the advanced gas turbine systems with water addition. In this paper, comprehensive available experimental data and calculation methods for the air-water mixture were reviewed. It is found that the available experimental data are limited, and the determined temperature is within 75 °C. New experimental data are needed to supply in order to verify the model further. Three kinds of models (ideal model, ideal mixing model and real model) were used to calculate saturated vapor composition and enthalpy for the air-water mixture, and the calculated results of these models were compared with experimental data and each other. The comparison shows that for the calculation of saturated vapor composition, the reliable range of the ideal model and ideal mixing model is up to 10 bar. The real model is reliable over a wide temperature and pressure range, and the model proposed by Hyland and Wexler is the best one of today. However, the reliability of the Hyland and Wexler model approved by experimental data is only up to 75 °C and 50 bar, and it is necessary to propose a new predictive model based on the available experimental data to be used up to elevated temperatures and pressures. In the calculation of enthalpy, compared to the ideal model, the calculated results of the ideal mixing model are closer to those of real model.

A model is used to calculate saturated thermophysical properties (humidity, entropy, and enthalpy) of a nitrogen-water mixture at elevated temperatures and pressures. In the model, a modified Redlich–Kwong equation of state is used to calculate fugacity coefficients for the vapor phase, and the liquid phase follows Henry's law. The model has been investigated by comparing the calculated results with the available experimental data. The comparison shows that the model can be used to calculate saturated thermodynamic properties for the nitrogen-water mixture reliably up to 523.15 K and 300 bar.

A new thermodynamic model was presented to calculate the phase equilibria for the oxygen-water system. The modified Redlich-Kwong equation of state with a new correlated cross-interaction parameter was used to calculate fugacity coefficients for the vapor phase. The dissolved oxygen followed Henry's law. A new expression was correlated from the experimental data to calculate Henry's constant of oxygen. The calculated results of equilibrium composition were compared with the available experimental data and those calculated by other models with different parameters. The comparison revealed that the new model is suitable for calculating both liquid and vapor compositions while the empirical method is only suitable for estimating the liquid composition. Furthermore, compared to the model proposed by Rebenovich and Beketov, the calculated results of the vapor composition with the new model are better.

A new thermodynamic model is proposed to calculate the thermodynamic properties for the air-water system in which the dry air was assumed to be a mixture of nitrogen and oxygen with the mole fractions of 0.7812 and 0.2188, respectively. For the vapor phase, fugacity coefficients were calculated with the modified Redlich-Kwong equation of state in which a new interaction parameter of oxygen and water was correlated from the experimental data of oxygen-water system. The dissolved gas followed Henry's law. Henry's constant of nitrogen was calculated with the Helgeson equation of state and that for oxygen was correlated from the experimental data of oxygen-water system. The proposed model was verified by comparing the calculated results with the available experimental data. It is shown that the proposed model is suitable for predicting saturated thermodynamic properties for the air-water system up to 300°C and 200 atm. Furthermore, the prediction results of the proposed model are better than those calculated with the model of Rabinovich and Beketov (Moist Gases, Thermodynamic Properties. Begell: House, 1995), and the application range is wider than that of the model of Hyland and Wexler (ASHRAE Trans. 89(2A) (1983a, b) 500-519, 520-535) which are among the best of today's models

For the needs of process design, the model proposed in our previous papers was extended to calculate the thermodynamic properties of humidity, heat capacity, molar volume, partial pressure of water vapour, enthalpy and entropy for humid gases (nitrogen, oxygen, air or a nitrogen-oxygen mixture). The comparison with other models from 300 to 473 K and I to 100 bar shows that the results calculated with different models are consistent within 50 bar and 400 K; out of this range, there is some difference. Meanwhile, mole ratios of nitrogen to oxygen in the saturated humid air were calculated from 323 to 523 K and 50 to 250 bar. It is found that the mole ratio of nitrogen to oxygen keeps almost constant, and the effect of the slight changes in the ratio of nitrogen to oxygen on the humidity, enthalpy and entropy of humid air is small enough to be neglected. Moreover, the enthalpy of dry air was predicted, and the comparison with other models again proved the reasonable assumptions and prediction capability of the new model

Ammonia-water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia-water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared, Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia-water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia-water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100 degreesC higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.

Gas turbines with air-water mixtures as the working fluid promise high electrical efficiencies and high specific power outputs to specific investment costs below that of combined cycles. Different humidified gas turbine cycles have been proposed, for example direct water-injected cycles, steam-injected cycles and evaporative cycles with humidification towers. However, only a few of these cycles have been implemented and even fewer are available commercially. This paper comprehensively reviews the literature on research and development on humidified gas turbines and identifies the cycles with the largest potential for the future. In addition, the remaining development work required for implementing the various humidified gas turbine cycles is discussed. This paper can also be used as a reference source that summarizes the research and development activities on humidified gas turbines in the last three decades.

This special issue of Applied Energy contains articles developed from initial ideas related to the 17th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES 2014) held in Prague, Czech Republic, during 23-27 August 2014. The conference has been organised jointly with CHISA 2014. Both events have benefitted from the shared pool of participants as well as the expanded opportunities for exchanging ideas. From all contributions presented at the conference, high-quality ones suitable for Applied Energy, have been invited. Overall, 37 extended manuscripts have been invited as candidate articles. Of those, after a thorough review procedure, 11 articles have been selected to be published. The topics attained in the focus of this Special Issue include Process Integration and Energy Management, CO2 capture, and Green Energy Applications.

Black liquor constitutes a huge energy potential. In order to improve the efficiency of a pulp mill, this study is focussed on borate autocausticizing, which has proved to work efficiently in recovery boilers. The leading idea is to complete an overloaded recovery boiler with a booster gasifier. In this configuration, the black liquor is gasified with air at low overpressure. Results regarding conventional black liquor gasification are close to the reality and very promising. Regarding black liquor gasification with borate, lack of data for orthoborate, like the Gibbs free energy, did not enable good results. The model so far is a good starting point for black liquor gasification studies, and needs to be improved as soon as new data on borates will be available.

Reducing energy consumption and increasing the use of renewable energy in the building sector are crucial to the mitigation of climate change. Wind power driven heat pumps have been considered as a sustainable measure to supply heat to the detached houses, especially those that even do not have access to the electricity grid. This work is to investigate the dynamic performance of a heat pump system driven by wind turbine through dynamic simulations. In order to understand the influence on the thermal comfort, which is the primary purpose of space heating, the variation of indoor temperature has been simulated in details. Results show that the wind turbine is not able to provide the electricity required by the heat pump during the heating season due to the intermittent characteristic of wind power. To improve the system performance, the influences of the capacity of wind turbine, the size of battery and the setpoint of indoor temperature were assessed. It is found that increasing the capacity of wind turbines is not necessary to reduce the loss of load probability; while on the contrary, increasing the size of battery can always reduce the loss of load probability. The setpoint temperature clearly affects the loss of load probability. A higher setpoint temperature results in a higher loss of thermal comfort probability. In addition, it is also found that the time interval used in the dynamic simulation has significant influence on the result. In order to have more accurate results, it is of great importance to choose a high resolution time step to capture the dynamic behaviour of the heat supply and its effect on the indoor temperature.

As a renewable energy, biogas produced from anaerobic digestion and landfill is playing a more and more important role in the energy market. Capturing CO2 from biogas can result in a negative CO2 emission. Depending on how biogas is utilized, there are different routes to capture CO2. A biogas plant that uses raw biogas to produce power and heat can be retrofitted by integrating CO2 capture. In order to identify the best option, three retrofits were compared from both technical and economic perspectives, including SYS-I, which captures CO2 from raw gas and produces biomethane instead of electricity and heat, SYS-II, which captures CO2 using MEA-based chemical absorption after the combustion of raw gas, and SYS-III, which captures CO2 by using oxy-fuel combustion of the raw gas. In general, SYS-I can achieve the highest profit and shortest payback time, mainly due to the high price of biomethane. SYSII and SYS-III are clearly influenced by carbon credit. In order to have positive profits for the retrofits of SYS-II and SYS-III, carbon credit needs to exceed 750SEK (or 100USD)/ton CO2 and 113 SEK (or 15USD)/ton CO2 respectively.

A conceptual system, mobilized thermal energy storage system (M-TES), was proposed for distributed heat supply. The economic evaluation that is essential to identify the key issues and provide guidelines regarding system improvement was conducted in this paper. Results show that the cost using M-TES to supply heat (COH) is primarily determined by the transport distance and the heat demand. The variation of COH is proportional to the transport distance, but inversely proportional to the heat demand. According to the sensitivity study, COH is more sensitive to the price of phase change material (PCM) than other parameters, such as the transport cost. Moreover, it is possible for an M-TES system to compete with other heat supply methods, such as pellet/bio-oil/biogas/oil boiler systems and electrical air-source heat pump. When using M-TES to replace the existing system, the payback time is mainly determined by the transport distance and the heat demand. Water is another potential working fluid for M-TES system. Comparatively, using PCM is more suitable for cases with larger heat demand or longer transport distance.

Reducing energy consumption and increasing use of renewable energy in the building sector are crucial to the mitigation of climate change. Wind power driven heat pumps have been considered as a sustainable measure to supply heat for detached houses, especially those that even don't have access to the grid. This work is to investigate the dynamic performance of a heat pump system directly driven by a wind turbine. The heat demand of a detached single family house was simulated in details. According to the simulations, the wind turbine is not able to provide the electricity demanded by the heat pump all the time due to the intermittent characteristic of wind power. To solve it, an electric energy storage system was included. Obviously, increasing the size of battery can always reduce the probability of load loss. However, different from the energy storage system, increasing the capacity of wind turbines is not necessary to reduce the probability of load loss instead, due to the different start-up speeds for different capacities of wind turbines. In order to maximize the system benefit, it is of great importance to optimize the capacity of the wind turbine and the size of the energy storage system simultaneously based on dynamic simulations.

Enhancing CO2 concentration in exhaust gas has been considered as a potentially effective method to reduce the penalty of electrical efficiency caused by CO2 chemical absorption in post-combustion carbon capture systems. Supplementary firing is an option that inherently has an increased CO2 concentration in the exhaust gas, albeit a relatively low electrical efficiency due to its increased mass flow of exhaust gas to treat and large temperature difference in heat recovery steam generator. This paper focuses on the methods that can improve the electrical efficiency of the supplementary fired combined cycles (SFCs) integrated with MEA-based CO2 capture. Three modifications have been evaluated: (I) integration of exhaust gas reheating, (II) integration of exhaust gas recirculation, and (III) integration of supercritical bottoming cycle. It is further showed that combining all three modifications results in a significant increase in electrical efficiency which is raised from 43.3% to 54.1% based on Lower Heating Value (LHV) of natural gas when compared to the original SFC. Compared with a conventional combined cycle with a subcritical bottoming cycle and without CO2 capture (56.7% of LHV), the efficiency penalty caused by CO2 capture is only 2.6% of LHV.

This article studied the integration of an evaporative gas turbine (EvGT) cycle with chemical absorption for CO2 capture. Two systems of EvGT cycle without CO2 capture and EvGT cycle with CO2 capture were simulated and optimized. The impacts of key parameters such as the water/air ratio (W/A), the stripper pressure, and the flue-gas condensing temperature were studied regarding the electrical efficiency and CO2 reduction. Simulation results show that (1) there always exists an optimum point of W/A for both EvGT and EvGT combined with CCS; (2) although lowering the stripper pressure would lower the heat quality requirement of reboiler, it increases the quantity more obviously. Therefore increasing the operating pressure of stripper would help to increase the total electrical efficiency; but the efficiency improvement becomes smaller if stripper pressure is high; (3) adding a flue-gas condenser to condense out the excessive water is another method to increase the total electrical efficiency. There is also an optimum point of condensing temperature considering the concentration of mono ethanol amine (MEA) and inlet temperature of stripper; and (4) comparatively the combined cycle has a higher gross electricity generation and electrical efficiency than the EvGT cycle no matter if combined with CO2 capture or not.

Oxyfuel combustion is a leading potential CO2 capture technology for power plants. As the flue gas (FG) consists of mainly H2O and CO2, a simpler and more energy-efficient CO2 purification method can be used instead of the standard amine-based chemical absorption approach. For the system of oxyfuel combustion with cryogenic CO2 purification, decreasing the oxygen purity reduces the energy consumption of the Air Separation Unit (ASU) but increases the energy consumption for the downstream cryogenic purification. Thus there exists a trade-off between the energy consumption of the ASU and that for cryogenic purification. This paper investigates the potential efficiency improvement by optimizing this trade-off. The simulated results show that there exists an optimum flue gas condensing pressure for the cryogenic purification, which is affected by the flue gas composition. In addition, decreasing the oxygen purity reduces the combined energy consumption of the ASU and the cryogenic purification, and therefore can improve the electrical efficiency. In summary, prior oxyfuel combustion analyses have assumed a high oxygen purity level of 95 mol% or 99 mol% for the combustion air, which achieves a high CO2 concentration in the flue gases. In this Paper, we demonstrate that a lower level of oxygen purity, such as 80 mol%, in conjunction with a more extensive cryogenic purification of the flue gases can lower the total energy consumption, thereby yielding a significant benefit. However, for oxygen purity levels lower than 75 mol%, it may not be possible to still use the two-stage flash system shown here to achieve a CO2 purity of 95 mol% and a CO2 recovery rate of 90% simultaneously.

The knowledge about pressure-volume-temperature-composition (PVTxy) properties plays an important role in the design and operation of many processes involved in CO(2) capture and storage (CCS) systems. A literature survey was conducted on both the available experimental data and the theoretical models associated with the thermodynamic properties of CO(2) mixtures within the operation window of CCS. Some gaps were identified between available experimental data and requirements of the system design and operation. The major concerns are: for the vapour-liquid equilibrium, there are no data about CO(2)/COS and few data about the CO(2)/N(2)O(4) mixture. For the volume property, there are no published experimental data for CO(2)/O(2), CO(2)/CO, CO(2)/N(2)O(4), CO(2)/COS and CO(2)/NH(3) and the liquid volume of CO(2)/H(2). The experimental data available for multi-component CO(2) mixtures are also scarce. Many equations of state are available for thermodynamic calculations of CO(2) mixtures. The cubic equations of state have the simplest structure and are capable of giving reasonable results for the PVTxy properties. More complex equations of state such as Lee-Kesler, SAFT and GERG typically give better results for the volume property, but not necessarily for the vapour-liquid equilibrium. None of the equations of state evaluated in the literature show any clear advantage in CCS applications for the calculation of all PVTxy properties. A reference equation of state for CCS should, thus, be a future goal.

Mitigation technologies including CO2 capture and storage in various energy conversion systems have been intensively developed in recent years. However, it is of importance to develop an equation of state (EOS) with simple structure and reasonable accuracy for engineering application for both pure CO2 and CO2 mixtures. In this paper, Redlich-Kwong equation of state was modified for gaseous CO2. In the new modification, parameter 'a' was correlated as a function of temperature and pressure from reliable experimental data in the range: 220K to 750K and 0.1MPa to 400MPa. To verify the accuracy of the new parameters, densities were calculated and compared with experimental data. The average error is 1.68 %. Other thermodynamic properties Of CO2, such as enthalpy and heat capacities, were also calculated; results fit experimental data well except critical region. This method can be further developed for CO2 mixture systems.

To develop an equation of state with simple structure and reasonable accuracy for engineering application, Redlich-Kwong equation of state was modified for gaseous CO2 and CO2-H2O mixtures. In the new modification, parameter 'a' of gaseous CO2 was regressed as a function of temperature and pressure from recent reliable experimental data in the range: 220-750 K and 0.1-400 MPa. Moreover, a new mixing rule was proposed for gaseous CO2-H2O mixtures. To verify the accuracy of the new modification, densities were calculated and compared with experimental data. The average error is 1.68% for gaseous CO2 and 0.93% for gaseous mixtures of CO2 and H2O, Other thermodynamic properties, such as enthalpy and heat capacities of CO2 and excess enthalpy of gaseous CO2-H2O mixtures, were also calculated; results fit experimental data well, except for the critical region.

Engineering calculation of the thermodynamic properties for cycle simulation and design requires simple but reliable models. This has been proved to be of importance for the research and development on humidified gas turbines, such as humid air turbine (HAT) cycles and compressed air energy storage (CAES). This paper has made a comprehensive review and comparison among different models for calculating thermodynamic properties of the humid air mixtures, including ideal gas model (IG), ideal mixing model (IM), and real gas model (RG); and based on temperature and pressure range, gave quantitative evaluations on saturated water vapor composition and enthalpy. Based on performance conditions of an HAT cycle, several suggestions were given for the use of the today's available models for engineering cycle calculations, which can provide accurate results for cycle performance analysis and design while keeping the methods straightforward.

Accurate experimental data on the thermo-physical properties of CO(2)-mixtures are pre-requisites for development of more accurate models and hence, more precise design of CO(2) capture and storage (CCS) processes. A literature survey was conducted on both the available experimental data and the theoretical models associated with the transport properties of CO(2)-mixtures within the operation windows of CCS. Gaps were identified between the available knowledge and requirements of the system design and operation. For the experimental gas-phase measurements, there are no available data about any transport properties of CO(2)/H(2)S, CO(2)/COS and CO(2)/NH(3); and except for CO(2)/H(2)O(/NaCl) and CO(2)/amine/H(2)O mixtures, there are no available measurements regarding the transport properties of any liquid-phase mixtures. In the prediction of gas-phase viscosities using Chapman-Enskog theory, deviations are typically <2% at atmospheric pressure and moderate temperatures. The deviations increase with increasing temperatures and pressures. Using both the Rigorous Kinetic Theory (RKT) and empirical models in the prediction of gas-phase thermal conductivities, typical deviations are 2.2-9%. Comparison of popular empirical models for estimation of gas-phase diffusion coefficients with newer experimental data for CO(2)/H(2)O shows deviations of up to 20%. For many mixtures relevant for CCS, the diffusion coefficient models based on the RKT show predictions within the experimental uncertainty. Typical reported deviations of the CO(2)/H(2)O system using empirical models are below 3% for the viscosity and the thermal conductivity and between 5 and 20% for the diffusion coefficients. The research community knows little about the effect of other impurities in liquid CO(2) than water, and this is an important area to focus in future work.

Proper solution of vapor liquid equilibrium (VLE) is essential to the design and operation of CO2 capture and storage system (CCS). According to the requirements of engineering applications, cubic equations of state (EOS) are preferable to predict VLE properties. This paper evaluates the reliabilities of five cubic EOSs, including PR, PT, RK, SRK and 3P1T for predicting VLE Of CO2 and binary CO2-mixtures containing CH4, H2S, SO2, Ar, N-2 or O-2, based on the comparisons with the collected experimental data. Results show that SRK is superior in the calculations about the saturated pressure of pure CO2; while for the VLE properties of binary CO2-mixtures, PR, PIT and SRK are generally superior to RK and 3P1T. The impacts of binary interaction parameter k(ij) were also analyzed. k(ij) has very clear effects on the calculating accuracy of an EOS in the property calculations Of CO2-mixtures. In order to improve the calculation accuracy, the binary interaction parameter was calibrated for all of the studied EOSs regarding every binary CO2-mixture.

Volume property is the necessary thermodynamic property in the design and operation of the CO2 Capture and storage system (CCS). Because of their simple structures, cubic equations of state (EOS) are preferable to be applied in predicting volumes for engineering applications. This paper evaluates the reliabilities of seven cubic EOS, including PR, PT, RK, SRK, MPR, MSRK and ISRK for predicting volumes of binary CO2 mixtures containing CH4, H2S, SO2, At and N-2, based on the comparisons with the collected experimental data. Results show that for calculations on the volume properties of binary CO2 mixtures, PR and PT are generally superior to others for all of the studied mixtures. In addition, it was found that the binary interaction parameter has clear effects on the calculating accuracy of an EOS in the volume calculations Of CO2 mixtures. In order to improve the accuracy, k(ij) was calibrated for all of the EOS regarding the gas and liquid phases of all the studied binary CO2 mixtures, respectively.

This article studied the integration of CO2 capture with evaporative gas turbine (EvGT) cycles. Two CO2 capture technologies are involved: MEA-based (monoethanolamine-based) chemical-absorption capture and O-2/CO2 recycle combustion capture. Based on them, three system configurations were analyzed: (1) EvGT cycle without CO2 capture, (2) EvGT cycle with chemical-absorption capture, and (3) EvGT cycle with O-2/CO2 recycle combustion capture. Simulation results show that the EvGT cycle with chemical-absorption capture has a higher electrical efficiency (39.73%) than the EvGT cycle with O-2/CO2 recycle combustion capture (37.45%). Compared with the EvGT cycle without CO2 capture, the penalty on electrical efficiency caused by CO2 capture is 11.91% if EvGT is combined with chemical-absorption capture, and 14.19% if EvGT is combined with O-2/CO2 recycle combustion capture. Moreover compared with combined cycles, EvGT cycles have a smaller gross electricity generation and a lower electrical efficiency no matter if they are combined with CO2 capture or not. Based on the analysis results of this article, several suggestions are also proposed to improve the net electrical efficiency of EvGT cycles with CO2 capture.

Solar thermal energy has the potential to supply the thermal demand of stripper reboiler in the power plant with amine-based post combustion CO2 capture. The performance of a power plant integrated with solar assisted post combustion CO2 capture (SCC) is largely affected by the local climatic conditions, such as solar irradiation, sunshine hours and ambient temperature, the type of solar thermal collector and CO2 recovery ratio. The feasibility evaluation results about such a power plant show that the cost of electricity (COE) and cost of CO2 avoidance (COA) are mainly determined by the local climatic conditions. For the locations having higher solar irradiation, longer sunshine hours and higher ambient temperature, the power plant with SCC has lower COE and COA. COE and COA are sensitive to the prices of solar thermal collectors. In order to achieve lower COE and COA compared to the power plant integrated with non-solar assisted post combustion capture, the price of solar thermal collector has to be lower than 150 USD/m(2) and 90 USD/m(2) for the solar trough and vacuum tube, respectively.

Based on the requirements of CO2 transportation and storage, non-condensable gases, such as O-2, N-2 and At should be removed from the CO2-stream captured from an oxy-fuel combustion process. For a purification process, impurities have great impacts on the design, operation and optimization through their impacts on the thermodynamic properties of CO2-streams. Study results show that the increments of impurities will make the energy consumption of purification increase: and make CO2 purity of separation product and CO2 recovery rate decrease, In addition, under the same operating conditions, energy consumptions have different sensitivities to the variation of the impurity mole fraction of feed fluids. The isothermal compression work is more sensitive to the variation of SO2: while the isentropic compression work is more sensitive to the variation of Ar. In the flash system, the energy consumption of condensation in is more sensitive to the variation of Ar; but in the distillation system, the energy consumption of condensation is more sensitive to the variation of SO2, and CO2 purity of separation is more sensitive to the variation of SO2.

Platinum-cobalt (Pt-Co) catalyst coatings are studied for preferential oxidation of carbon monoxide (PROX) ill hydrogen-rich gas streams. Experimental results show a role for cobalt in improving catalytic activity. The most active catalyst coating can decrease carbon monoxide concentrations from 1% to a value of less than 10 ppm for GHSV values ranging from 40,000 to 120,000 ml g(-1) h(-1). This catalyst coating can work at a wide window of operation ill terms of temperature. Transmission electron microscopy, selected-area electron diffraction, and diffuse reflectance infrared Fourier transform spectroscopy show that the addition of Co forms Pt3Co intermetallic compounds and slightly increases the average particle size. In situ laser Raman spectroscopy reveals the co-existence of Co metal and its oxides on the catalyst surface, due to gradual oxidation of Co by gas phase oxygen within the initial stage of the PROX reaction. The promotional effect of Co during PROX is confirmed and ascribed to this Pt3Co intermetallic compound and the synergetic effect of Co-0 and Co chi+. The high accessibility of the reactant to Pt3Co species appears favorable and crucial for PROX.

To reduce the peak load, dynamic electricity price schemes have been widely used. Refrigerated warehouses consume a large amount of energy, most of which happens during the daytime due to the higher ambient temperature. This work evaluated the potential benefits of integrating energy storage in the refrigerated warehouses. Two types of energy storage systems have been considered, including a cold energy storage system and an electrical energy storage system. A dynamic model has been developed in TRNSYS to study the performance of those two energy storage systems and assess the benefits. Results show that using the cold energy storage to shift power consumption from daytime to nighttime can increase the energy efficiency of the refrigeration system. However, as the electrical energy storage system can shift more power consumption, it can achieve a large cost saving. Compared to the reference system without energy storage, the introductions of a cold energy storage system and an electrical energy storage system can reduce the operational cost by 10 and 53.7% respectively.

Key Performance Indicators (KPIs) are important for monitoring the performance in the industry. They can be used to identify poor performance and the improvement potential. KPIs can be defined for individual equipment, sub-processes, and whole plants. Different types of performances can be measured by KPIs, for example energy, raw-material, control & operation, maintenance, etc. Benchmarking KPIs with KPIs from similar equipment and plants is one method of identifying poor performing areas and estimating improvement potential. Actions for performance improvements can then be developed, prioritized and implemented based on the KPIs and the benchmarking results. An alternative to benchmarking, which is described in this paper, is to identify the process signals that are strongest correlated with the KPI and then change these process signals in the direction that improves the KPI. This method has been applied to data from a combined heat and power plant and a suggestion are given on how to improve boiler efficiency. (C) 2015 The Authors. Published by Elsevier Ltd.

China is a coal-based energy consuming country. The proportion of coal is up to 70% in the energy consumption structure in 1990s. In the past 20 years, driven by energy saving policy, China's energy consumption structure has undergone great changes, especially in urban areas. This paper explores the evolution of energy-use structure at the national level and the level of Beijing City in China. Four major energy sources were considered, including coal, oil, natural gas and electricity. The dataset was collected from 1990 to 2012. The results show that the proportion of coal consumption decreased by approximately 20% from 1990 to 2012 at the national level in compare with nearly 50% at the level of Beijing City. Furthermore, the proportion of natural gas consumption and other clean energies rose. In Beijing the natural gas and other clean energies account for over 60% of the total energy in 2012, which played an important role in improving the local environment.

Lignocellulosic biomass is a renewable feedstock that has the potential to replace the diminishing fossil fuels. Herein, we reported the simultaneous conversion of cellulose, hemicellulose and lignin from raw biomass into gasoline alkanes (hexanes and pentanes) and monophenols and related hydrocarbons over layered LiTaMoO6 and Ru/C in aqueous phosphoric acid medium. Specifically, gasoline alkanes were directly yielded from the carbohydrate components, based on hemicellulose and cellulose, and the total yield could be up to 82.4%. Notably, the lignin fraction could also be transformed into monophenols, related alcohols and hydrocarbons by the one-pot reaction. It suggested that the hydrocracking of monophenol fraction could be performed in this catalytic system. The total yield of volatile products was 53% based on the lignin fraction. In this paper, the influences of phosphoric acid concentration, substrate ash and the amino acids derived from the biogenic impurities were investigated and different raw biomass substrates were tested. Furthermore, the catalysts could be reused for several runs to convert raw biomass without pretreatment.

International trade has become the fastest growing driver of global carbon emissions, with large quantities of emissions embodied in exports from emerging economies. International trade with emerging economies poses a dilemma for climate and trade policy: to the extent emerging markets have comparative advantages in manufacturing, such trade is economically efficient and desirable. However, if carbon-intensive manufacturing in emerging countries such as China entails drastically more CO2 emissions than making the same product elsewhere, then trade increases global CO2 emissions. Here we show that the emissions embodied in Chinese exports, which are larger than the annual emissions of Japan or Germany, are primarily the result of China's coal-based energy mix and the very high emissions intensity (emission per unit of economic value) in a few provinces and industry sectors. Exports from these provinces and sectors therefore represent targeted opportunities to address the climate-trade dilemma by either improving production technologies and decarbonizing the underlying energy systems or else reducing trade volumes.

The global warming and energy crisis have att racted signifi cant att ention round the world in recent years. As a basic social unit involving building construction, inhabitant transportation, energy utilization, and individual behavior, the community may signifi cantly aff ect the carbon emissions generated by humans. The concept of low carbon community has been accordingly proposed to reduce global greenhouse gas emissions and accelerate a prosperous low carbon economy. In this paper, various low carbon technologies, strategies, and lifestyles, involving community planning, advanced green building technologies, renewable energy supply systems, sustainable transportation, water recycle and waste management systems, change of low carbon living mode and energy-related behavior were thoroughly discussed. The current status of low carbon community practices in both developed countries and China, together with their corresponding achievements, has been reviewed. Evaluation tools and indicators were analyzed to provide important references for policy makers in supporting sustainable community construction activities. Furthermore, recommendations were proposed to facilitate the development of low carbon communities in the future.